Generally, wind turbine systems are devices that covert kinetic energy from the wind into electric energy, and are typically classified into onshore wind turbine systems and offshore wind turbine systems, according to the condition of the environment in which the wind turbine system is installed.
FIG. 1 is a schematic view showing the structure of a general wind turbine system. The operation of the wind turbine system will be described in brief with reference to FIG. 1.
First, a tower 40 is set up on a solid ground 50 using a concrete structure or the like, and a nacelle 20 is seated on the tower 40. A gearbox 22, a generator 24, an inverter, a transformer, and others are provided in the nacelle 20. Blades 30 are coupled and secured to the gearbox 22 via a hub and a main shaft. The blades 30, which are rotated at low speed by the wind, generate kinetic energy of high speed of 1500 rpm or more via the gearbox 22, and the generator 24 converts the kinetic energy into electric energy. Electricity produced by the generator 24 is rectified by the inverter and then is transmitted.
The above regular conversion of energy in wind power generation causes a loss in the form of heat. The energy may be lost when the generator converts kinetic energy into electric energy, and may be lost by gear friction in the gearbox that is a driving line. Further, heat caused by the loss of energy may be generated in rectifying devices such as the inverter or the transformer.
If additional heat loss occurs in a power cable, a control cabinet, and a power supply for coupling respective devices to each other in the nacelle, heat loss is further increased undesirably.
Among the existing onshore wind turbine systems, in the case of generating a small capacity of electricity and thus generating a smaller amount of heat in the nacelle, the inside of the generator may be cooled by introducing external air into the nacelle. Meanwhile, as for the offshore wind turbine systems, in the case of using the generator, the gearbox, the inverter, etc. in a coastal environment, they may be damaged by corrosion because the external air contains salt.